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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Dorsal view of a Zapada cinctipes (Nemouridae) (Tiny Winter Black) Stonefly Nymph from the Yakima River in Washington
Nymphs of this species were fairly common in late-winter kick net samples from the upper Yakima River. Although I could not find a key to species of Zapada nymphs, a revision of the Nemouridae family by Baumann (1975) includes the following helpful sentence: "2 cervical gills on each side of midline, 1 arising inside and 1 outside of lateral cervical sclerites, usually single and elongate, sometimes constricted but with 3 or 4 branches arising beyond gill base in Zapada cinctipes." This specimen clearly has the branches and is within the range of that species.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Willmilne has attached this picture to aid in identification. The message is below.
Manitoba Canada

Posts: 19
Willmilne on Jul 3, 2008July 3rd, 2008, 10:38 am EDT

Found some of these lovely nymphs while out - any suggestions as to species?



Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on Jul 3, 2008July 3rd, 2008, 12:04 pm EDT
My first impression is that it is a Maccaffertium (formerly Stenonema) nymph. That said, however, you have some heptageniids up there with which I am not at all familiar. It is a very striking specimen and ripe to hatch (a "blackwing"). Perhaps Roger or Konchu can offer another opinion.
Taxon's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on Jul 3, 2008July 3rd, 2008, 7:15 pm EDT

These are the two Heptageniid nymphs on Will's website. I arranged them similarly aligned for comparison purposes.

In late May, I suggested the one on the left was probably Leucrocuta maculipennis. My guess is that the one on the right may be either Heptagenia flavescens or Maccaffertium modestum. How's that for hedging?

In any event, Will certainly does have a talent for photographing aquatic insects.
Best regards,
Roger Rohrbeck
Manitoba Canada

Posts: 19
Willmilne on Jul 4, 2008July 4th, 2008, 3:39 am EDT
Thanks for the suggestions on ID.So much to learn. I guess I have to start learning to photograph the key details and get a little more focused. I am at the moment simply taken with the beauty and subtle variations of color in these, sometimes at first glance , rather drab looking insects. Glad you are enjoying the pics Roger.

Would you think this is the same species at a different stage, the markings are very similar - it was collected at the same time. Much lighter and more yellow olive in tone and lacking the lower leg banding.



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"Bear Swamp," PA

Posts: 1681
GONZO on Jul 4, 2008July 4th, 2008, 6:10 am EDT

The photo in the link does appear to be the same species, but not as "ripe" yet. Overall, I am leaning toward a Maccaffertium ID because the gills look more like that genus than Heptagenia to me.

By the way, I came across a recent article in the Journal of Insect Science that proposed a new species, Heptagenia whitingi (considered a sister taxon of H. flavescens). The dorsal photo included in the article appeared to match the markings of your other specimen (the one on the left in Roger's comparison) almost exactly, except that it is a paler version (probably due to preservation in alcohol). What first caught my attention was the mention of the large, pale rectangular markings on abdominal tergum 4 as an important diagnostic character. (However, please note the comment about H. adaequata in the larval diagnosis.) The other interesting aspect was the use of DNA "barcoding." It's just a thought, but you can find the article at:


(I wish I could make that a direct link, but I can't seem to get BBCode to work here. My computer skills suck, so I'm probably doing something wrong.)
Avondale PA

Posts: 2
Dhfunk on Nov 15, 2008November 15th, 2008, 5:51 am EST
H. whitingi seems reasonable for the one on the left. The one on the right looks a perfect match for Stenonema femoratum. If you were to flip the specimen over and find a series of dark sublateral spots on each side of the abdominal segments, that would nail it.
Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on Nov 15, 2008November 15th, 2008, 7:30 am EST
Nice of you to pick up on this one, David. I sometimes forget to consider femoratum now that it is stranded on its own. The illustration in Spieth (of "S. femoratum tripunctatum," 1947) and especially the photo in Lewis (of "S. tripunctatum," 1974) do look very much like Will's other specimen. Thanks for pointing things in the right direction!

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